Spin element and magnetic memory

ABSTRACT

A spin element includes an element portion including a first ferromagnetic layer, a conducting portion that extends in a first direction as viewed in a lamination direction of the first ferromagnetic layer and faces the first ferromagnetic layer, and a current path extending from the conducting portion to a semiconductor circuit and having a resistance adjusting portion between the conducting portion and the semiconductor circuit, wherein the resistance value of the resistance adjusting portion is higher than the resistance value of the conducting portion, and the temperature coefficient of the volume resistivity of a material forming the resistance adjusting portion is lower than the temperature coefficient of the volume resistivity of a material forming the conducting portion.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 16/475,478, filed Jul. 2, 2019, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a spin element and a magnetic memory.Priority is claimed on Japanese Patent Application No. 2018-042135,filed Mar. 8, 2018, the content of which is incorporated herein byreference.

Description of Related Art

A giant magnetoresistance (GMR) element including a multilayer film offerromagnetic and nonmagnetic layers, and a tunnel magnetoresistance(TMR) element using an insulating layer (a tunnel barrier layer or abarrier layer) as a nonmagnetic layer are known. These are attractingattention as elements for magnetic sensors, high frequency components,magnetic heads, and nonvolatile random access memories (MRAMs).

In the case of an MRAM, data is read from and written to it by utilizingthe characteristic that the resistance of a GMR element or a TMR elementchanges as the magnetization direction of two ferromagnetic layerssandwiching an insulating layer therebetween changes. Known writingschemes of an MRAM include a scheme in which writing (magnetizationreversal) is performed using a magnetic field generated by a current anda scheme in which writing (magnetization reversal) is performed using aspin transfer torque (STT) generated by causing a current to flow in thelamination direction of a magnetoresistive element.

The magnetization reversal of a TMR element using an STT is efficientfrom the viewpoint of energy efficiency, but the reversal currentdensity for causing the magnetization reversal is high. It is desirablethat the reversal current density be low from the viewpoint of a longlife of the TMR element. The same applies to a GMR element.

In recent years, therefore, attention has been focused on magnetizationreversal using a spin orbit torque (SOT) as a means for reducing thereversal current with a mechanism different from an STT. For example,Non-Patent Document 1 describes an SOT type magnetoresistive elementusing an SOT. An SOT is induced by a pure spin current generated by thespin Hall effect or an interfacial Rashba effect at the interface ofdifferent materials. A current for inducing an SOT in a magnetoresistiveelement is caused to flow in a direction intersecting the laminationdirection of the magnetoresistive element. Thus, in an SOT-MRAM, it isunnecessary to cause a current to flow through the tunnel barrier layerof the TMR element and it is expected that the life of amagnetoresistive element will be able to be extended.

In addition, a spin that contributes to magnetization reversal isintroduced through the junction surface between a TMR element and an SOTwiring layer. Whether or not the magnetization is reversed in theferromagnetic material of the TMR element is determined by the currentdensity of a current flowing through the SOT wiring. A current densityrequired to reverse the magnetization of the ferromagnetic material iscalled a critical current density.

Patent Documents

[Non-Patent Document 1] S. Fukami, T. Anekawa, C. Zhang and H. Ohno,Nature Nano Tech (2016). DOI: 10.1038/NNANO. 2016.29

SUMMARY OF THE INVENTION

Here, the resistance value of the SOT wiring fluctuates depending ontemperature. When the resistance value fluctuates, the current densityof a current flowing through the SOT wiring fluctuates with the samevoltage being applied. The fluctuation of the current density of acurrent flowing through the SOT wiring causes a decrease in writeprobability or causes back hopping. Further, such phenomena are notlimited to an SOT type magnetoresistive element using an SOT, and thesame applies to a domain wall motion type magnetic recording elementusing the movement of a domain wall.

The present invention has been made in view of the above problems and itis an object of the present invention to provide a spin element and amagnetic memory with improved operation stability in ranges of differenttemperatures.

The present invention provides the following means to solve the aboveproblems.

(1) A spin element according to a first aspect includes an elementportion including a first ferromagnetic layer, a conducting portion thatextends in a first direction as viewed in a lamination direction of thefirst ferromagnetic layer and faces the first ferromagnetic layer, and acurrent path extending from the conducting portion to a semiconductorcircuit and having a resistance adjusting portion in a middle of thecurrent path, wherein a resistance value of the resistance adjustingportion is higher than a resistance value of the conducting portion, anda temperature coefficient of volume resistivity of a material formingthe resistance adjusting portion is lower than a temperature coefficientof volume resistivity of a material forming the conducting portion.

(2) In the spin element according to the above aspect, the resistanceadjusting portion may include a plurality of resistance adjusting partsthat are disposed apart from each other, the plurality of resistanceadjusting parts may include a first resistance adjusting portion and asecond resistance adjusting portion, the first resistance adjustingportion may be disposed in a current path between a first end of theconducting portion in the first direction and a first semiconductorcircuit, and the second resistance adjusting portion may be disposed ina current path between a second end of the conducting portion in thefirst direction and a second semiconductor circuit.

(3) In the spin element according to the above aspect, the resistanceadjusting portion may include a plurality of resistance adjusting partsthat are disposed apart from each other, the resistance adjustingportion may be within a range of an outer shape of the conductingportion in a plan view in the lamination direction, and at least one ofthe plurality of resistance adjusting parts may extend in the firstdirection.

(4) In the spin element according to the above aspect, the resistanceadjusting portion may include a plurality of resistance adjusting partsthat are disposed apart from each other, at least one of the pluralityof resistance adjusting parts may be disposed outside a range of anouter shape of the conducting portion in a plan view in the laminationdirection, and the resistance adjusting part disposed outside the rangeof the outer shape may extend in an in-plane direction orthogonal to thelamination direction.

(5) In the spin element according to the above aspect, the plurality ofresistance adjusting parts may all extend in the first direction, and atleast a part of the plurality of resistance adjusting parts may bedisposed at a depth position different from that of the conductingportion.

(6) In the spin element according to the above aspect, the resistanceadjusting portion is made of a material selected from the groupconsisting of Ni—Cr, platinum rhodium, Chromel, Incoloy and stainlesssteel.

(7) In the spin element according to the above aspect, the conductingportion may be a spin-orbit torque wiring configured to apply a spinorbit torque to a magnetization of the first ferromagnetic layer torotate the magnetization of the first ferromagnetic layer, and theelement portion may consist of the first ferromagnetic layer.

(8) In the spin element according to the above aspect, the conductingportion may be a spin-orbit torque wiring configured to apply a spinorbit torque to a magnetization of the first ferromagnetic layer torotate the magnetization of the first ferromagnetic layer, and theelement portion may have the first ferromagnetic layer, a nonmagneticlayer, and a second ferromagnetic layer in order of increasing distancefrom the conducting portion.

(9) In the spin element according to the above aspect, the conductingportion may be a magnetic recording layer having a domain wall, and theelement portion may have a nonmagnetic layer and the first ferromagneticlayer in order of increasing distance from the magnetic recording layer.

(10) A magnetic memory according to a second aspect includes a pluralityof spin elements according to the first aspect.

According to the spin element of the present invention, stable operationcan be performed even in ranges of different temperatures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically showing a spin-orbit-torque(SOT) type magnetization rotational element according to a firstembodiment.

FIG. 2 is a schematic cross-sectional view of a configuration includingthe SOT type magnetization rotational element shown in FIG. 1 .

FIG. 3 is a schematic plan view of an SOT type magnetization rotationalelement according to a second embodiment.

FIG. 4A is a schematic plan view of an SOT type magnetization rotationalelement according to a modification of the second embodiment.

FIG. 4B is a schematic side view of an SOT type magnetization rotationalelement as viewed in the direction of arrow A in FIG. 4A.

FIG. 5 is a schematic plan view of an SOT type magnetization rotationalelement according to a third embodiment.

FIG. 6 is a perspective view schematically showing an SOT typemagnetoresistive element according to a fourth embodiment.

FIG. 7 is a perspective view schematically showing a domain wall motiontype magnetic recording element according to a fifth embodiment.

FIG. 8 is a cross-sectional view schematically showing the domain wallmotion type magnetic recording element according to the fifthembodiment.

FIG. 9 is a plan view of a magnetic recording array according to a sixthembodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the embodiments will be described in detail with referenceto the drawings as appropriate. In the drawings used in the followingdescription, to make features of the present invention easy tounderstand, some portions corresponding to the features are shownenlarged for the sake of convenience and the dimensional proportions orthe like between components may be different from those of the actualones. Materials, dimensions, or the like provided in the followingdescription are merely exemplary examples and the present invention isnot limited thereto and can be carried out by appropriately changingthem within a range in which the effects of the present invention areexhibited.

(Spin-Orbit-Torque (SOT) Type Magnetization Rotational Element)

[First embodiment]

FIG. 1 is a perspective view schematically showing an SOT typemagnetization rotational element 100 according to a first embodiment ofthe present invention. The SOT type magnetization rotational element isan example of the spin element.

The SOT type magnetization rotational element 100 has a firstferromagnetic layer 1, an SOT wiring 5, and a current path 10 (10A,10B). The SOT wiring 5 is an example of the conducting portion. Thefirst ferromagnetic layer 1 is an example of the element portion. InFIG. 1 , a semiconductor circuit 30 connected to the SOT typemagnetization rotational element 100 is also shown. The SOT wiring 5extends in a first direction (X direction) as viewed in the direction oflamination of the first ferromagnetic layer 1 (Z direction). That is,the SOT wiring 5 has a long axis in the X direction in a plan view inthe Z direction. The SOT wiring 5 faces the first ferromagnetic layer 1.Here, facing refers to a facing relationship in which the two layers maybe in contact with each other or may have another layer therebetween.The current path 10 (10A, 10B) electrically connects the SOT wiring 5and the semiconductor circuit 30 (a first semiconductor circuit 30A anda second semiconductor circuit 30B).

The current path 10 (10A, 10B) includes a resistance adjusting portion11 (a first resistance adjusting portion 11A and a second resistanceadjusting portion 11B) between the SOT wiring 5 and the semiconductorcircuit 30. The resistance value of the resistance adjusting portion 11is higher than the resistance value of the SOT wiring 5. The temperaturecoefficient of the volume resistivity of a material forming theresistance adjusting portion 11 is lower than the temperaturecoefficient of the volume resistivity of a material forming the SOTwiring 5.

The semiconductor circuit 30 is a circuit provided to cause a current toflow in the SOT wiring 5 and is, for example, a transistor (see FIG. 2). The semiconductor circuit 30 is external to the SOT typemagnetization rotational element 100.

FIG. 2 is a cross-sectional view of the SOT type magnetizationrotational element 100 shown in FIG. 1 to which an example of thesemiconductor circuit 30 is added. The semiconductor circuit 30 shown inFIG. 2 includes a transistor 30A (with a source and drain S/D and a gateelectrode G), a transistor 30B (with a source and drain S/D and a gateelectrode G), vias 121A and 121B connected thereto, and bit lines BL1and BL2.

When the transistors 30A and 30B are turned on to apply a predeterminedpotential difference between the bit lines BL1 and BL2, a current flowsbetween the bit line BL1 and the bit line BL2. For example, a currentflows through the bit line BL1, the via 121A, the transistor 30A, thevia 21A-2, the first resistance adjusting portion 11A, and the via 21A-1in this order and is then supplied to a first end 5 a of the SOT wiring5. In contrast, a current may also flow though the bit line BL2, the via121B, the transistor 30B, the via 21B-2, the second resistance adjustingportion 11B, and the via 21B-1 in this order and be then supplied to asecond end 5 b of the SOT wiring 5.

When a current flows in the SOT wiring 5, a pure spin current isgenerated in the SOT wiring 5. The pure spin current supplies spins tothe first ferromagnetic layer 1 via a junction surface 1 a between thefirst ferromagnetic layer 1 and the SOT wiring 5. The supplied spinsgive a spin orbit torque (SOT) to the magnetization of the firstferromagnetic layer 1.

In this specification, the “current path” refers to a path through whichcurrent flows. A typical example of the “current path” in thisspecification is a via or a wiring. On the other hand, the “currentpath” in this specification does not include a current path resultingfrom a parasitic capacitance or a parasitic inductance and a currentpath of a minute current flowing in an insulator. A via is a connectionregion that electrically connects lower and upper layer wirings inmultilayer wirings. A via is formed by etching an interlayer insulatingfilm to open a via hole and filling the via hole with a metal material.In this specification, a via and a wiring may be collectively referredto as a via wiring. The “current path” in this specification includes acurrent path having a via wiring and a resistance adjusting portion anda current path that having a via wiring, a resistance adjusting portionand other components.

In this specification, a “semiconductor circuit external to the element”refers to a semiconductor circuit that is first reached when a currentpath connected to the SOT wiring (the conducting portion) is followedfrom the SOT wiring. In other words, the “semiconductor circuit” in thisspecification refers to a semiconductor circuit closest to the SOTwiring on the current path. Accordingly, in the example shown in FIG. 1, the current paths 10A and 10B between the SOT wiring 5 and thesemiconductor circuit 30 are the current path of the via 21A-1, thefirst resistance adjusting portion 11A, and the via 21A-2 which aredisposed between the SOT wiring 5 and the transistor 30A, and thecurrent path of the via 21B-1, the second resistance adjusting portion11B, and the via 21B-2 which are disposed between the SOT wiring 5 andthe transistor 30B, respectively. Thus, the via 121A and the via 121Bare not included in the “current paths between the SOT wiring and thesemiconductor circuit.”

<First Ferromagnetic Layer>

The first ferromagnetic layer 1 includes a ferromagnetic material. Forexample, a metal selected from the group consisting of Cr, Mn, Co, Feand Ni, an alloy containing at least one of these metals, or an alloycontaining these metals and at least one element of B, C, and N can beused as a ferromagnetic material forming the first ferromagnetic layer1. Specific examples of the ferromagnetic material are Co—Fe, Co—Fe—B,and Ni—Fe.

The material forming the first ferromagnetic layer 1 may also be aHeusler alloy. The Heusler alloy is a half-metal and has high spinpolarization. The Heusler alloy is an intermetallic compound having achemical composition of XYZ or X₂YZ. X is a transition metal element ora noble metal element of Co, Fe, Ni or Cu groups in the periodic table.Y is a transition metal element of Mn, V, Cr or Ti groups or the sameelement as X. Z is a typical element of Groups III to V. Examples of theHeusler alloy include Co₂FeSi, Co₂FeGe, Co₂FeGa, Co₂MnSi,Co₂Mn_(1-a)Fe_(a)Al_(b)Si_(1-b), and Co₂FeGe_(1-c)Ga_(c).

The first ferromagnetic layer 1 may be an in-plane magnetization filmhaving an easy magnetization axis in the in-plane direction of XY or aperpendicular magnetization film having an easy magnetization axis inthe Z direction. The magnetization easy axis may also be inclined withrespect to the Z direction.

The film thickness of the first ferromagnetic layer 1 is preferably 2.5nm or less, more preferably 2.0 nm or less, when the magnetization easyaxis of the first ferromagnetic layer 1 is in the Z direction (such thatit is a perpendicular magnetization film). To secure a sufficient amountof magnetization, the film thickness of the first ferromagnetic layer 1is preferably 1.0 nm or more. When the film thickness of the firstferromagnetic layer 1 is reduced, the first ferromagnetic layer 1 hasperpendicular magnetic anisotropy (interface perpendicular magneticanisotropy) under the influence of the interface between the firstferromagnetic layer 1 and the other layers.

<SOT Wiring>

The SOT wiring 5 extends in the X direction. The SOT wiring 5 faces onesurface of the first ferromagnetic layer 1 in the Z direction. The SOTwiring 5 may be directly connected to the first ferromagnetic layer 1 ormay be connected thereto via another layer.

When a layer is interposed between the SOT wiring 5 and the firstferromagnetic layer 1, the layer interposed between the SOT wiring 5 andthe first ferromagnetic layer 1 is preferably made of a material thatdoes not easily dissipate spins propagating from the SOT wiring 5. Forexample, it is known that silver, copper, magnesium, and aluminum have along spin diffusion length of 100 nm or more and do not easily dissipatespins.

The thickness of this layer is preferably equal to or less than the spindiffusion length of the material forming the layer. If the thickness ofthe layer is equal to or less than the spin diffusion length, spinspropagating from the SOT wiring 5 can be sufficiently transferred to thefirst ferromagnetic layer 1.

The SOT wiring 5 is made of a material in which a spin current isgenerated by the spin Hall effect when a current flows. A materialconfigured to generate a spin current in the SOT wiring 5 is sufficientas such a material. Accordingly, this material is not limited to amaterial composed of a single element and may include a part made of amaterial in which a spin current is generated and a part made of amaterial in which a spin current is hardly generated.

The spin Hall effect is a phenomenon in which when a current flows in awiring, a spin current is induced in a direction orthogonal to thedirection of the current on the basis of the spin-orbit interaction.When a current flows in the wiring, a first spin oriented in onedirection and a second spin oriented in the opposite direction to thefirst spin are bent in the direction orthogonal to the current. A spincurrent is induced in a direction of eliminating the uneven distributionof the first and second spins. The ordinary Hall effect and the spinHall effect are the same in that moving (traveling) charges (electrons)are bent in the moving (traveling) direction. On the other hand, in theordinary Hall effect, charged particles moving in a magnetic field arebent in the moving direction under a Lorentz force, whereas in the spinHall effect, electrons are bent in the moving direction only due totheir movement (current flowing) even in the absence of a magneticfield, which is a great difference from the ordinary Hall effect.

In a nonmagnetic material (nonferromagnetic material), the number ofelectrons of the first spin and the number of electrons of the secondspin are equal. Therefore, the number of electrons of the first spintoward a first surface of the SOT wiring 5 on which the firstferromagnetic layer 1 is disposed and the number of electrons of thesecond spin S2 toward the opposite direction to the first surface areequal. In this case, the flows of charge cancel each other out and theamount of current becomes zero. A spin current without this current isparticularly called a pure spin current.

When the flow of electrons of the first spin, the flow of electrons ofthe second spin, and the spin current are denoted by J_(↑), J_(↓), andJ_(S), respectively, the spin current is defined such thatJ_(S)=J_(↑)−J_(↓). J_(S) flows in one direction as a pure spin current.Here, J_(S) is a flow of electrons with a polarizability of 100%.

The main component of the SOT wiring 5 is preferably a nonmagnetic heavymetal. Here, the term “heavy metal” is used to indicate a metal having aspecific gravity equal to or higher than that of yttrium. The SOT wiring5 may be made of only a nonmagnetic heavy metal.

It is preferable that the nonmagnetic heavy metal be a nonmagnetic metalhaving a high atomic number of 39 or more and having d or f electrons inthe outermost shell. Nonmagnetic heavy metals have a great spin-orbitinteraction that causes the spin Hall effect. The SOT wiring 5 may bemade of only a nonmagnetic metal having a high atomic number of 39 ormore and having d or f electrons in the outermost shell.

Normally, electrons move in a direction opposite to the direction of thecurrent regardless of the directions of spins. However, a nonmagneticmetal having a high atomic number and having d or f electrons in theoutermost shell has a great spin-orbit interaction, such that the spinHall effect acts strongly. Therefore, the direction of movement ofelectrons depends on the directions of spins of electrons. Thus, a spincurrent J_(S) is easily generated in such nonmagnetic heavy metals.

The SOT wiring 5 may also contain a magnetic metal. “Magnetic metal”indicates a ferromagnetic metal or an antiferromagnetic metal. When theantiferromagnetic metal contains a small amount of magnetic metal, itbecomes a spin scattering factor. When spins are scattered, thespin-orbit interaction is enhanced and the efficiency of spin currentgeneration of a current flowing through the SOT wiring 5 is increased.The SOT wiring 5 may also be made of only an antiferromagnetic metal.

Since the spin-orbit interaction is caused by an intrinsic internalfield of the material of the SOT wiring, a pure spin current is alsogenerated in a nonmagnetic material. If a trace amount of a magneticmetal is added to the SOT wiring, the magnetic metal scatters electrons(spins) flowing through the material. As a result, the efficiency ofspin current generation of the SOT wiring 5 is improved. However, if theamount of the magnetic metal added is excessively increased, the addedmagnetic metal scatters the generated spin current, which may result inincreasing the effect of decreasing the spin current. Therefore, it ispreferable that the mole fraction of the added magnetic metal besufficiently smaller than the mole fraction of the main element of thespin generating portion in the SOT wiring. It is preferable that themole fraction of the added magnetic metal be roughly 3% or less.

The SOT wiring 5 may also include a topological insulator. The SOTwiring 5 may be made of only a topological insulator. The topologicalinsulator is a material which is internally an insulator or a highresistance body but causes a spin-polarized metallic state on thesurface thereof. In this material, an internal magnetic field isgenerated by the spin-orbit interaction. Therefore, even if there is noexternal magnetic field, a new topological phase arises in the materialdue to the effect of the spin-orbit interaction. This is a topologicalinsulator which can generate a pure spin current with high efficiencydue to a strong spin-orbit interaction and breaking of reversal symmetryat the edge.

The topological insulator is preferably, for example, SnTe,Bi_(1.5)Sb_(0.5)Te_(1.7)Se_(1.3), TlBiSe₂, Bi₂Te₃, Bi_(1-x)Sb_(x),(Bi_(1-x)Sb_(x))₂Te₃, or the like. These topological insulators arecapable of generating a spin current with high efficiency.

<Resistance Adjusting Portion>

The resistance adjusting portion 11 is located in the middle of thecurrent path 10 between the SOT wiring and the semiconductor circuit. Inother words, the resistance adjusting portion 11 constitutes the currentpath 10 as a part of the current path 10 between the SOT wiring 5 andthe semiconductor circuit 30.

The resistance adjusting portion 11 may be formed of one part. Forexample, in FIGS. 1 and 2 , the resistance adjusting portion 11 mayinclude only the first resistance adjusting portion 11A or only thesecond resistance adjusting portion 11B. The resistance adjustingportion 11 may also be formed of a plurality of resistance adjustingparts that are disposed apart from each other. For example, as shown inFIGS. 1 and 2 , the plurality of resistance adjusting parts may have thefirst resistance adjusting portion 11A and the second resistanceadjusting portion 11B. When the resistance adjusting portion 11 includesa plurality of resistance adjusting parts, adjacent resistance adjustingparts are connected together through a via wiring.

The resistance adjusting portion 11 is formed of two resistanceadjusting parts that are disposed apart from each other in the exampleshown in FIGS. 1 and 2 , but may also be formed of three or moreresistance adjusting parts.

When the resistance adjustment portion is formed of a plurality ofresistance adjusting parts that are disposed apart from each other, thedegree of freedom in design of the entire resistance value of theresistance adjustment portion is increased. On the other hand, when theresistance adjusting portion is formed of one part, the fabrication iseasy.

In the example shown in FIGS. 1 and 2 , the resistance adjusting portion11 (the first resistance adjusting portion 11A and the second resistanceadjusting portion 11B) is connected to the SOT wiring 5 through vias.The resistance adjusting portion 11 is not limited to this case and maybe directly connected to the SOT wiring 5 without vias.

Further, in the example shown in FIGS. 1 and 2 , the first resistanceadjusting portion 11A and the second resistance adjusting portion 11Bare electrically connected to the first end 5 a and the second end 5 bthat are ends in the X direction which is the longitudinal direction ofthe SOT wiring 5 through the via 21A-1 and the via 21B-1, respectively.The first resistance adjusting portion 11A and the second resistanceadjusting portion 11B may also be connected directly or indirectly toportions other than the first end 5 a and the second end 5 b.

Moreover, in the example shown in FIG. 1 and FIG. 2 , the resistanceadjusting portion 11 (the first resistance adjusting portion 11A and thesecond resistance adjusting portion 11B) is that with which a membercorresponding to a wiring in a normal via wiring is substituted.However, the resistance adjusting portion 11 may also be that with whicha member corresponding to a via or a member other than a via wiringwhich constitutes a current path is substituted.

The resistance adjusting portion 11 has a resistance value higher thanthat of the SOT wiring 5.

Here, the resistance value is represented by equation R=ρL/A (where R isthe resistance value, ρ is the resistivity, L is the length, and A isthe cross-sectional area). The resistance value can be freely designedby changing at least one or two of the resistivity (volume resistivity),the length, and the cross-sectional area.

Further, the temperature coefficient of the volume resistivity of thematerial forming the resistance adjusting portion 11 is lower than thetemperature coefficient of the volume resistivity of the materialforming the SOT wiring 5.

Here, the “temperature coefficient of the volume resistivity” in thisspecification is calculated as α_(0,100)={(ρ₁₀₀−ρ₀)/ρ₀}×100 when thevolume resistivity at 0° C. is ρ₀ and that at 100° C. is ρ₁₀₀.

The SOT type magnetization rotational element 100 can stably supply anappropriate value of current to the SOT wiring by including theresistance adjusting portion 11. As a result, it is possible to preventa decrease in write probability due to a decrease in write current orback hopping due to an increase in current.

For example, a material selected from the group consisting of Ni—Cr,platinum rhodium, Chromel, Incoloy, and stainless steel can be used asthe material of the resistance adjusting portion 11.

These materials have a low rate of change of the volume resistivity at100° C. with respect to the volume resistivity at 0° C. (the temperaturecoefficient as defined above), which is 15% or less for all of them, 10%or less for materials other than platinum rhodium, and 4% or less forNi—Cr, Chromel and Incoloy.

[Second embodiment]

FIG. 3 is a schematic plan view of an SOT type magnetization rotationalelement 200 according to a second embodiment of the present invention asviewed in the Z direction.

Hereinafter, features of the SOT type magnetization rotational element200 according to the second embodiment will be described. The samereference signs are assigned to components common with the SOT typemagnetization rotational element 100 according to the first embodimentand a description thereof will be omitted.

In the SOT type magnetization rotational element 200, a resistanceadjusting portion 12 is formed of two resistance adjusting parts 12A and12B that are disposed apart from each other. The resistance adjustingportion 12 is within the range of an outer shape 5A of an SOT wiring 5in a plan view in the Z direction. The two resistance adjusting parts12A and 12B extend in the same X direction as the direction in which theSOT wiring 5 extends.

When the resistance adjusting portion 12 is within the range of theouter shape 5A of the SOT wiring 5, the SOT type magnetizationrotational elements can be densely arranged and thus the degree ofintegration of the entire element is increased. Further, the resistanceof the resistance adjusting portion 12 can be increased since theresistance adjusting portion 12 extends long in the extending directionof the SOT wiring 5 (X direction).

In the SOT type magnetization rotational element 200 shown in FIG. 3 ,both the two resistance adjusting parts 12A and 12B constituting theresistance adjusting portion 12 extend in the same X direction as theextending direction of the SOT wiring 5. However, only one of the tworesistance adjusting parts 12A and 12B may extend in the X direction.Even in this case, the resistance of the one resistance adjusting partcan be increased.

FIG. 4A is a schematic plan view of an SOT type magnetization rotationalelement 200A according to a modification of the second embodiment. FIG.4B is a schematic side view of FIG. 4A as viewed in the direction ofarrow A.

The SOT type magnetization rotational element 200A of this modificationdiffers from the configuration shown in FIG. 3 in that a plurality ofresistance adjusting parts extending in the same X direction as theextending direction of the SOT wiring are provided at different depthpositions.

Specifically, the resistance adjusting part 12A has two resistanceadjusting parts. These resistance adjusting parts 12A-1 and 12A-2 arelocated at different depth positions. Similarly, the resistanceadjusting part 12B has two resistance adjusting parts. These tworesistance adjusting parts are located at positions overlapping theresistance adjusting parts 12A-1 and 12A-2 in FIG. 4B. That is, theresistance adjusting portion 12 includes four resistance adjustingparts.

Resistance adjusting parts that are adjacent in the depth direction (forexample, the resistance adjusting parts 12A-1 and 12A-2) are connectedtogether through a via.

The number of resistance adjusting parts is four in the example shown inFIGS. 4A and 4B, but may be three or may be five or more. Resistanceadjusting parts need not be arranged symmetrically. Resistance adjustingparts may be disposed at different depth positions of three or morelayers. When each depth is counted as one layer, the resistanceadjusting parts are in one layer in the example shown in FIG. 3 and arein two layers in the example shown in FIG. 4 .

By providing resistance adjusting parts constituting the resistanceadjusting portion at two or more depths (that is, in two or morelayers), the length of the resistance is made longer as compared withthe configuration in which they are provided only in one layer. That is,the entire resistance value of the resistance adjusting portion can beincreased.

The configuration in which resistance adjusting parts constituting theresistance adjusting portion are provided at different depths (indifferent layers) may also be applied to other embodiments.

[Third embodiment]

FIG. 5 is a schematic plan view of an SOT type magnetization rotationalelement 300 according to a third embodiment as viewed in the Zdirection.

Hereinafter, features of the SOT type magnetization rotational element300 according to the third embodiment will be described. The samereference signs are assigned to components common with the SOT typemagnetization rotational element 100 according to the first embodimentand the SOT type magnetization rotational elements 200 and 200Aaccording to the second embodiment and a description thereof will beomitted.

In the SOT type magnetization rotational element 300, a resistanceadjusting portion 13 includes two resistance adjusting parts 13A and 13Bthat are disposed apart from each other. At least a part of theresistance adjusting parts 13A and 13B is disposed outside the range ofan outer shape 5A of an SOT wiring 5 in a plan view in the laminationdirection (Z direction). The two resistance adjusting parts 13A and 13Bextend in an in-plane direction (in the in-plane direction of XY)orthogonal to the lamination direction (Z direction).

Here, the disposition of resistance adjusting parts constituting theresistance adjusting portion outside the range of the outer shape 5A ofthe SOT wiring 5 in a plan view in the lamination direction (Zdirection) means disposition of least a part of the resistance adjustingparts outside the range of the outer shape of the SOT wiring. Forexample, the resistance adjusting part 13A shown in FIG. 5 includes afirst part 13A-1 and a second part 13A-2. The first part 13A-1 is aportion that is connected to a via 23A-1 and extends in the Y direction.The second part 13A-2 is a portion that extends in the X direction froman end of the first part 13A-1 which is not connected to the via 23A-1.The second part 13A-2 is disposed outside the range of the outer shapeof the SOT wiring. One portion (a solid line portion) of the first part13A-1 is disposed outside the range of the outer shape, while anotherportion (a dotted line portion) thereof is disposed within the range ofthe outer shape. Similarly, the resistance adjusting part 13B is formedof a first part 13B-1 and a second part 13B-2. The first part 13B-1 is aportion that is connected to a via 23B-1 and extends in the Y direction.The second part 13B-2 is a portion that extends in the X direction froman end of the first part 13B-1 which is not connected to the via 23B-1.The second part 13B-2 is disposed outside the range of the outer shapeof the SOT wiring. One portion (a solid line portion) of the first part13B-1 is disposed outside the range of the outer shape, while anotherportion (a dotted line portion) thereof is disposed within the range ofthe outer shape.

When the resistance adjusting parts 13A and 13B constituting theresistance adjusting portion are arranged outside the range of the outershape 5A of the SOT wiring 5 in a plan view in the lamination direction(Z direction), the lengths thereof are increased by the portions (thefirst part 13A-1 and the second part 13B-2 in the example of FIG. 5 )which protrude outside the range of the outer shape 5A from the viasdisposed directly below the SOT wiring 5, as compared with theconfiguration in which they are arranged inside the range of the outershape 5A. That is, the entire resistance value of the resistanceadjusting portion can be increased.

Also in the SOT type magnetization rotational element according to thethird embodiment, a plurality of resistance adjusting parts constitutingthe resistance adjusting portion may be provided at different depths (indifferent layers).

[Fourth embodiment]

(SOT Type Magnetoresistive Element)

FIG. 6 is a perspective view schematically showing an SOT typemagnetoresistive element 500 according to a fourth embodiment.

The SOT type magnetoresistive element 500 has a first ferromagneticlayer 1, a nonmagnetic layer 2, a second ferromagnetic layer 3, an SOTwiring 5, and a current path 10 (10A and 10B). The SOT wiring 5 is anexample of the conducting portion. A structure 20 which is a combinationof the first ferromagnetic layer 1, the nonmagnetic layer 2, and thesecond ferromagnetic layer 3 is an example of the element portion. InFIG. 6 , a semiconductor circuit 30 connected to the SOT typemagnetoresistive element 500 is also shown. The SOT wiring 5 extends inthe first direction (X direction) as viewed in the direction oflamination of the first ferromagnetic layer 1 (Z direction). The SOTwiring 5 faces the first ferromagnetic layer 1. The nonmagnetic layer 2faces a surface of the first ferromagnetic layer 1 opposite to the SOTwiring 5. The second ferromagnetic layer 3 faces a surface of thenonmagnetic layer 2 opposite to the first ferromagnetic layer 1. Thecurrent path 10 (10A, 10B) electrically connects the SOT wiring 5 andthe semiconductor circuit 30 (a first semiconductor circuit 30A and asecond semiconductor circuit 30B). The current path 10 (10A, 10B)includes a resistance adjusting portion 11 (a first resistance adjustingportion 11A and a second resistance adjusting portion 11B) between theSOT wiring 5 and the semiconductor circuit 30. The resistance value ofthe resistance adjusting portion 11 is higher than the resistance valueof the SOT wiring 5. The temperature coefficient of the volumeresistivity of a material forming the resistance adjusting portion 11 islower than the temperature coefficient of the volume resistivity of amaterial forming the SOT wiring 5.

The structure 20 which is a combination of the first ferromagnetic layer1, the nonmagnetic layer 2 and the second ferromagnetic layer 3 is thestructure of a normal magnetoresistive element, and thus a layerstructure included in a normal magnetoresistive element can be appliedto the structure 20.

<Second ferromagnetic layer>

The SOT type magnetoresistive element 500 functions by the magnetizationof the second ferromagnetic layer 3 being fixed in one direction and thedirection of the magnetization of the first ferromagnetic layer 1 beingrelatively changed. In the case of application to a coercivitydifference type (pseudo spin valve type) MRAM, the coercivity of thesecond ferromagnetic layer 3 is made greater than the coercivity of thefirst ferromagnetic layer 1. In the case of application to an exchangebias type (spin valve type) MRAM, the magnetization direction of thesecond ferromagnetic layer 3 is fixed by exchange coupling with theantiferromagnetic layer.

The SOT type magnetoresistive element 500 is a tunnelingmagnetoresistance (TMR) element when the nonmagnetic layer 2 is made ofan insulator and a giant magnetoresistance (GMR) element when thenonmagnetic layer 2 is made of a metal.

The lamination structure of a known magnetoresistive element can beadopted as the lamination structure of the SOT type magnetoresistiveelement 500. For example, each layer may be formed of a plurality oflayers and another layer such as an antiferromagnetic layer may beprovided to fix the magnetization direction of the second ferromagneticlayer 3. The second ferromagnetic layer 3 corresponds to a fixed layeror a reference layer and the first ferromagnetic layer 1 corresponds toa layer that is called a free layer, a storage layer or the like.

A known material can be used as the material of the second ferromagneticlayer 3 and the same material as the first ferromagnetic layer 1 canalso be used. Since the first ferromagnetic layer 1 is an in-planemagnetization film, the second ferromagnetic layer 3 is also preferablyan in-plane magnetization film.

To increase the coercivity of the second ferromagnetic layer 3 withrespect to the first ferromagnetic layer 1, an antiferromagneticmaterial such as IrMn or PtMn may be used as a material in contact withthe second ferromagnetic layer 3. To prevent a leakage magnetic field ofthe second ferromagnetic layer 3 from affecting the first ferromagneticlayer 1, a synthetic ferromagnetic coupling structure may also be used.

<Nonmagnetic layer>

Known materials can be used for the nonmagnetic layer 2. For example,when the nonmagnetic layer 2 is made of an insulator (i.e., when thenonmagnetic layer 2 is a tunnel barrier layer), Al₂O₃, SiO₂, MgO,MgAl₂O₄, or the like can be used as a material for the nonmagnetic layer2. Besides these materials, a material in which a part of Al, Si, or Mgis substituted with Zn, Be, or the like can also be used for thenonmagnetic layer 2. Among them, MgO and MgAl₂O₄ can efficiently injectspins since these are materials capable of realizing coherent tunneling.When the nonmagnetic layer 2 is made of a metal, Cu, Au, Ag, or the likecan be used as a material for the nonmagnetic layer 2. Further, when thenonmagnetic layer 2 is made of a semiconductor, Si, Ge, CuInSe₂,CuGaSe₂, Cu(In, Ga)Se₂, or the like can be used as a material for thenonmagnetic layer 2.

[Fifth embodiment]

(Domain Wall Motion Type Magnetoresistive Element)

FIG. 7 is a perspective view schematically showing a domain wall motiontype magnetic recording element 600 according to a fifth embodiment.FIG. 8 is a cross-sectional view schematically showing the domain wallmotion type magnetic recording element 600 according to the fifthembodiment.

The domain wall motion type magnetic recording element 600 has a firstferromagnetic layer 1, a nonmagnetic layer 4, a magnetic recording layer5′, and a current path 10 (10A, 10B). The magnetic recording layer 5′ isan example of the conducting portion. A structure 40 which is acombination of the first ferromagnetic layer 1 and the nonmagnetic layer4 is an example of the element portion. In FIGS. 7 and 8 , asemiconductor circuit 30 connected to the domain wall motion typemagnetic recording element 600 is also shown. The fifth embodiment isthe same as the embodiments described above except that the conductingportion is the magnetic recording layer 5′ and the element portion isthe structure 40, and a description of the same configuration will beomitted.

The magnetic recording layer 5′ extends in the first direction (Xdirection) as viewed in the direction of lamination of the firstferromagnetic layer 1 (Z direction). The magnetic recording layer 5′faces the first ferromagnetic layer 1. The nonmagnetic layer 4 islocated between the first ferromagnetic layer 1 and the magneticrecording layer 5′. The current path 10 (10A, 10B) electrically connectsthe magnetic recording layer 5′ and the semiconductor circuit 30 (afirst semiconductor circuit 30A and a second semiconductor circuit 30B).The current path 10 (10A, 10B) includes a resistance adjusting portion11 (a first resistance adjusting portion 11A and a second resistanceadjusting portion 11B) between the magnetic recording layer 5′ and thesemiconductor circuit 30. The resistance value of the resistanceadjusting portion 11 is higher than the resistance value of the magneticrecording layer 5′. The temperature coefficient of the volumeresistivity of a material forming the resistance adjusting portion 11 islower than the temperature coefficient of the volume resistivity of amaterial forming the magnetic recording layer 5′.

The magnetic recording layer 5′ internally has a domain wall DW. Adomain wall DW is the boundary between two magnetic domains havingmagnetizations in opposite directions. The domain wall motion typemagnetic recording element 600 records data in multiple values accordingto the position of the domain wall DW in the magnetic recording layer5′. The data recorded in the magnetic recording layer 5′ is read as achange in the resistance value in the lamination direction of the firstferromagnetic layer 1 and the magnetic recording layer 5′.

The domain wall DW moves when a current flows through the magneticrecording layer 5′. When the position of the domain wall DW changes, themagnetization state of the magnetic recording layer 5′changes. Thedomain wall motion type magnetic recording element 600 outputs, as data,a change in the resistance value associated with a change in therelative angle of the magnetizations of the two magnetic materials (thefirst ferromagnetic layer 1 and the magnetic recording layer 5′)sandwiching the nonmagnetic layer 4 therebetween.

The magnetic recording layer 5′includes a magnetic material. The samemagnetic material as that of the first ferromagnetic layer 1 can be usedas the magnetic material forming the magnetic recording layer 5′. Themagnetic recording layer 5′ preferably contains at least one elementselected from the group consisting of Co, Ni, Pt, Pd, Gd, Tb, Mn, Ge,and Ga. Examples of this are a laminated film of Co and Ni, a laminatedfilm of Co and Pt, a laminated film of Co and Pd, a MnGa based material,a GdCo based material, and a TbCo based material. Ferrimagneticmaterials such as the MnGa based material, the GdCo based material, andthe TbCo based material have small saturation magnetization and canlower a threshold current necessary to move the domain wall DW. Thelaminated film of Co and Ni, the laminated film of Co and Pt, and thelaminated film of Co and Pd have great coercivity and can suppress themoving speed of the domain wall DW.

The SOT type magnetization rotational element, the SOT typemagnetoresistive element, and the domain wall motion type magneticrecording element have so far been provided as specific exemplaryexamples of the spin element. These are the same in that a write currentflows in the conducting portion (the SOT wiring 5 and the magneticrecording layer 5′) extending in the direction intersecting the firstferromagnetic layer 1 at the time of data writing. The spin element isnot limited to these elements as long as a write current flows in theconducting portion extending in the direction intersecting the elementportion at the time of data writing.

[Sixth embodiment]

(Magnetic Memory)

A magnetic memory according to a sixth embodiment includes a pluralityof spin elements. For example, the magnetic memory according to thepresent invention includes a plurality of SOT type magnetoresistiveelements.

FIG. 9 is a plan view of a magnetic recording array 700 according to thesixth embodiment. The magnetic recording array 700 shown in FIG. 9 has a3×3 matrix arrangement of SOT type magnetization rotational elements100. FIG. 9 shows an example of the magnetic recording array, where SOTtype magnetization rotational elements 100 may be replaced with otherspin elements and the number and arrangement of spin elements arearbitrary.

One word line WL 1 to WL 3, one bit line BL 1 to BL 3, and one read lineRL 1 to RL 3 are connected to each SOT type magnetization rotationalelement 100.

By selecting a word line WL1 to WL3 and a bit line BL1 to BL3 to whichto apply current, a current flows in an SOT wiring 5 of an arbitrary SOTtype magnetization rotational element 100 to perform a write operation.Further, by selecting a read line RL1 to RL3 and a bit line BL1 to BL3to which to apply current, a current flows in the lamination directionof an arbitrary SOT type magnetization rotational element 100 to performa read operation. A word line WL1 to WL3, a bit line BL1 to BL3, and aread line RL1 to RL3 to which to apply current can be selected bytransistors or the like.

Although preferred embodiments of the present invention have beendescribed above in detail, the present invention is not limited to thespecific embodiments and various modifications and changes may be madewithout departing from the spirit and scope of the present invention asset forth in the claims.

EXPLANATION OF REFERENCES

1 First ferromagnetic layer

2, 4 Nonmagnetic layer

3 Second ferromagnetic layer

5 SOT wiring

5′ Magnetic recording layer

10, 10A, 10B Current path

11, 12, 13 Resistance adjusting portion

11A First resistance adjusting portion

11B Second resistance adjusting portion

30 Semiconductor circuit

20, 40 Structure (element portion)

100, 200, 200A, 300 SOT type magnetization rotational element

500 SOT type magnetoresistive element

600 Domain wall motion type magnetic recording element

700 Magnetic recording array

What is claimed is:
 1. A spin element comprising: an element portionincluding a first ferromagnetic layer; a conducting portion that extendsin a first direction as viewed in a lamination direction of the firstferromagnetic layer and faces the first ferromagnetic layer; and acurrent path extending from the conducting portion to a semiconductorcircuit and comprising a resistance adjusting portion between theconducting portion and the semiconductor circuit, wherein a resistancevalue of the resistance adjusting portion is higher than a resistancevalue of the conducting portion, and at least a part of the resistanceadjusting portion is disposed outside the range of an outer shape of theconducting portion when viewed from a second direction orthogonal to thefirst direction.
 2. The spin element according to claim 1, wherein thesecond direction is the lamination direction.
 3. The spin elementaccording to claim 1, wherein the second direction is orthogonal to thelamination direction and the first direction.
 4. The spin elementaccording to claim 1, wherein the resistance adjusting portion includesa plurality of resistance adjusting parts that are disposed apart fromeach other; the plurality of resistance adjusting parts include a firstresistance adjusting portion and a second resistance adjusting portion,the first resistance adjusting portion is disposed in a current pathbetween a first end of the conducting portion in the first direction anda first semiconductor circuit, and the second resistance adjustingportion is disposed in a current path between a second end of theconducting portion in the first direction and a second semiconductorcircuit.
 5. The spin element according to claim 4, wherein the pluralityof resistance adjusting parts all extend in the first direction, and atleast a part of the plurality of resistance adjusting parts is disposedat a depth position different from that of the conducting portion. 6.The spin element according to claim 4, wherein the resistance adjustingportion is made of a material selected from the group consisting ofNi—Cr, platinum rhodium, Chromel, Incoloy and stainless steel.
 7. Thespin element according to claim 1, wherein the conducting portion is aspin-orbit torque wiring configured to apply a spin orbit torque to amagnetization of the first ferromagnetic layer to rotate themagnetization of the first ferromagnetic layer, and the element portionconsist of the first ferromagnetic layer.
 8. The spin element accordingto claim 1, wherein the conducting portion is a spin-orbit torque wiringconfigured to apply a spin orbit torque to a magnetization of the firstferromagnetic layer to rotate the magnetization of the firstferromagnetic layer, and the element portion comprises the firstferromagnetic layer, a nonmagnetic layer, and a second ferromagneticlayer in order of increasing distance from the conducting portion. 9.The spin element according to claim 1, wherein the conducting portion isa magnetic recording layer having a domain wall, and the element portioncomprises a nonmagnetic layer and the first ferromagnetic layer in orderof increasing distance from the magnetic recording layer.
 10. A magneticmemory comprising a plurality of spin elements according to claim 1.